core: Update certificates as late as possible

  This changes aims minimize the unecessary accessed to master while the
  instance is going to be skipped to process or won't post informations to master.

  This in best cases reduces access from 1+n to 1 while n = number of used partitions.

slapos/grid/SlapObject.py

@@ -452,7 +452,6 @@ class Partition(object):
           self.partition_id + '.key')
       self.cert_file = os.path.join(certificate_repository_path,
           self.partition_id + '.crt')
-      self._updateCertificate()
 
     try:
       self.retention_delay = float(retention_delay)
@@ -485,6 +484,9 @@ class Partition(object):
                                       required=bytes2human(required)))
 
   def _updateCertificate(self):
+    if getattr(self, "key_file", None) is None:
+      return 
+
     try:
       partition_certificate = self.computer_partition.getCertificate()
     except NotFoundError:

slapos/grid/slapgrid.py

@@ -954,9 +954,11 @@ stderr_logfile_backups=1
     except PromiseError as e:
       self.logger.error(e)
       if partition_access_status is None or not status_error:
+        local_partition._updateCertificate()
         computer_partition.error(e, logger=self.logger)
     else:
       if partition_access_status is None or status_error:
+        local_partition._updateCertificate()
         computer_partition.started()
 
   def processPromise(self, computer_partition):
@@ -1184,6 +1186,9 @@ stderr_logfile_backups=1
       self.logger.info('  Software path: %s' % software_path)
       self.logger.info('  Instance path: %s' % instance_path)
 
+      # Update certifcate at late as possible
+      local_partition._updateCertificate()
+
       # XXX this line breaks 37 tests
       # self.logger.info('  Instance type: %s' % computer_partition.getType())
       self.logger.info('  Instance status: %s' % computer_partition_state)
@@ -1788,6 +1793,7 @@ stderr_logfile_backups=1
             ipv4_global_network=self.ipv4_global_network,
           )
           local_partition.stop()
+          local_partition._updateCertificate()
           try:
             computer_partition.stopped()
           except (SystemExit, KeyboardInterrupt):